Forensic Dentistry, Second Edition

204 Forensic dentistry

of the perpetrator, photographs frequently are the only permanent record of

the injuries to the victims. Therefore, it is imperative that the forensic investi-

gator be able to properly photograph injury patterns as a means of preserving

such evidence.

This chapter is better understood if the reader has a good grasp of photo-

graphic terminology and the skills for operating basic camera equipment. It is

not the authors’ intent to attempt to cover basic photography. There are many

publications that can provide the necessary background to improve one’s

understanding of the photographic principles described in this chapter. Two

readily available and easy reading books are Basic Photography by Michael

Langford^1 and The Basic Book of Photography, Fifth Edition, by Tom Grimm.^2

This chapter will provide an overview of the various techniques utilized

by t he forensic dent a l photog rapher to properly record i nju r ies u si ng adva nced

photographic methods. It will also present the historical photo graphic tech-

niques utilizing traditional film and the exploding era of digital imaging.

11.2 The Spectrum of Light

The process of photographically recording images on film, videotape, or
magnetic media occurs through the capture of electromagnetic radiation
(light) of specific wavelengths. These wavelengths are measured in millionths
of millimeters, referred to as nanometers (nm). Photographic images can be
recorded on film emulsions that are sensitive to light wavelengths anywhere
between 250 and 900 nm. Visible light, which we see with our unaided human
eye, comprises only from 400 to 760 nm. Most modern digital cameras and
traditional photographic films are specifically designed to record images
seen in the visible range of light as we see them However, it is also possible
to record images we cannot see when specifically illuminated in the shorter
ultraviolet range (210 to 400 nm) and longer infrared range (750 to 900 nm).
Since ultraviolet and infrared radiations are outside the visible range of the
spectrum, they are commonly referred to as nonvisible light. Recent genera-
tions of digital cameras have been designed to allow the recording of pat-
terned injuries in skin using both visible light and nonvisible light. While
the electronic transfer of light to magnetic recording media is very different
than exposing photographic film, for the most part, the techniques utilized
for image capture are basically the same. Photography using nonvisible light
requires special techniques to record the injury, including an occasional
minor focusing adjustment called focus shift^3 that provides correction for
the optical properties of lenses that were designed primarily to be used for
visible light photography (Table 11.1).